A trial-cosed effectiveness study of subcutaneous immunitherapy in adults

Aim: To perform a cost‐effectiveness analysis (CEA) of subcutaneous immunotherapy (SCIT) in combination with symptomatic medication as needed (Intervention group) compared to treatment with symptomatic medication alone (Control group) in patients with allergic rhinitis sensitized to grass pollen, and/or tree pollen, and/or house dust mite. The cost‐effectiveness is assessed from a societal as well as from a healthcare perspective. Methods: Trial‐based CEA, with results obtained from a multicenter randomized controlled open‐label clinical trial. Three patient cohorts were included in the trial respectively in 2009, 2010 and 2011 with follow‐up times of two, two and one year, respectively. The included patients were randomized over the two treatment arms, SCIT with symptomatic treatment as needed and symptomatic medication alone. Information regarding the resource use (costs) and health‐related quality of life (HRQoL, effects) was collected by means of scheduled questionnaires. The timing of the questionnaires was based on allergen exposition levels in previous years. Included patients were categorized according to their allergen sensitizations to grass pollen, tree pollen and house dust mite and all combinations of these. Health utilities were derived from the generic EQ‐5D, SF‐36v2 (SF‐6D) questionnaires and from a disease specific questionnaire using a visual analogue scale (VAS). They were recalculated into quality‐adjusted life years (QALYs). An annual global assessment (GA) questionnaire was used to assess treatment success. A generalized estimated equation (GEE) model was introduced to explain and predict costs and effects. The predicted costs and effects were used to determine the incremental cost‐effectiveness ratio (ICER) per QALY gained and an ICER per successfully treated patient. A non‐parametric bootstrap is performed to obtain uncertainty intervals around the costs and effect. The results are plotted in cost‐effectiveness planes and acceptability curves. A subgroup analysis for the subgroups tree pollen, grass pollen and house dust mite was performed. Results: 183 patients were enrolled into the trial, 156 patient of these 183 filled out at least one cost and effect questionnaire, and could be used in the cost‐effectiveness analysis. A majority of the patients suffered from multiple sensitizations (57.1% in the SCIT group and 55.9% in the Control group). SCIT has a small, positive and significant (P=0.05) effect on the mean VAS scores within the SCIT treatment group when compared to the Control group. No significant effect of SCIT treatment could be determined on the health related quality of life as measured by the EQ‐5D and SF‐6D questionnaires. No ICER could be calculated due to the lack of cost savings in the SCIT treatment group based on these questionnaires. The subgroup analysis for the three main allergen groups offered no new insights. A positive treatment effect of SCIT could be observed (P<0.10) when subjective treatment success was based on the results of the GA questionnaire.